In Luke 5:36, Jesus introduced a second argument on this subject. He referred to a physical truth in order to make an important spiritual point (i.e., He used a parable). The new garment He spoke of was symbolic of the new dispensation Jesus was working to introduce. The old garment represented Judaism. As He had already explained, it was illogical for His disciples to mourn at this time, and for Him to instruct them to fast and mourn while He was present was comparable to tearing a piece off a new garment in order to patch up an old one. In so doing, the new garment would be damaged and the old would not be restored to its former condition. If Jesus' disciples fasted, they would be acting contrary to the spirit of the new age and their actions would not be helpful to Judaism in any way. To unite fasting and mourning with the joyous work of Jesus' disciples while He was still with them would have been utter foolishness. Jesus clearly was not a reformer of Judaism. He created a new and better "garment" and had no intentions of patching up the old one (cf. Heb. 8:6ff).
Jesus used a different illustration starting in Luke 5:37 to reiterate the same point He had been making. If new wine (i.e., grape juice) was to be successfully stored in a wineskin (i.e., a container usually made of the hides of goats), then the wineskin itself must be new. Under regular conditions, grape juice would naturally ferment. The fermentation process would break the wineskin if it wasn't flexible and able to stretch. New wineskins had the ability to expand to accommodate the fermentation of the new wine, but old skins did not. They would eventually burst if a fermenting liquid was placed inside them. Judaism could not contain the power of the new covenant that Jesus was establishing. The old wineskins would be discarded for the new.
However, with those thoughts in mind, what is the meaning of the Lord's statement in Luke 5:39? "And no one, having drunk old wine, immediately desires new; for he says, 'The old is good.'" Jesus had come along with His teachings and practices (i.e., His "new wine") and most Jews liked the "old wine" much better (i.e., Judaism). Their senses were dull and they were unable to discern the superior nature of the "new wine." They were comfortable with Judaism because they grew up with it and had practiced it as a people for over 1400 years. It was familiar to them and they were reluctant to change, and that is the very reason why they were fasting. It was simply their tradition to do so. Jesus' methods and teachings often conflicted with their traditions and they failed to realize that the newness He brought was so much better than what they currently possessed! Essentially, Jesus taught here that there is a time to fast, but the period in which He was on Earth was not that time. Why would anyone want to mourn and fast while the Messiah was present? The very presence of Jesus was worth celebrating! Sadly, the Jews were satisfied with the status quo even though they should have opened their eyes and embraced the beautiful newness that Christ was making possible.